Giant Crocodile

A giant crocodile on the party's side is a druid's wild shape, an animal companion grown beyond its station, or a swamp god's gift to a tribe the party has sworn to protect. Run it as a barge with teeth. The crocodile does what crocodiles do, which is wait in the water and then explode out of it, and the party's job is to maneuver enemies onto the shoreline.

The mechanical pull is the swim speed of 50 ft. paired with Stealth +5 and a 30 ft. walk. In any encounter that touches a river, lake, or coastal flat, the crocodile gets to choose when it appears and where. Position it submerged before initiative, and let the party set up the bait. With Strength 21 and a +5 Athletics-style modifier, it wins almost every grapple contest against Medium foes and most against Large, which makes it an excellent way to hold a single bridge or ford against a single big enemy while the party deals with everything else.

With AC 14 and 85 HP, it is durable for its CR but not invincible, and it has no magical resistance or speed boost to escape if the fight goes wrong. Pull it back into the water the moment it drops below half HP. Submerged, with Stealth +5, most pursuers will lose track of it. The crocodile is not a frontline tank; it is a powerful ambusher that the party uses for one decisive moment per encounter.

The detail that makes the giant crocodile feel like a creature, not a vehicle, is the eye. Describe the eye breaking the surface of the water, then the ridge of the back, then nothing. Players who can't see it where they expect to see it start moving carefully, and that's the whole point.

A giant crocodile in the river is the encounter the party doesn't realize they are in until someone fails a Perception check. It is a 50 ft. swim, +5 Stealth, Huge ambush predator with Passive Perception 10. The fight begins underwater, with one PC missing.

Open with the grab. While the party is fording, drinking, washing, or just standing too close to the bank, the crocodile uses its Strength 21 to make a grapple attempt against the closest target. Once a creature is in its mouth and underwater, that creature is in serious trouble: drowning rules, no easy way to attack, and the rest of the party is on the bank with no swim speeds. The whole encounter is built around a 30-second window where one PC needs to be rescued before they drown.

Damage matters less than control. The crocodile's job is to drag the grappled creature into deep water and submerge. The party has to spend their actions diving in, breaking the grapple with an opposed Strength check or matching DC, and getting their friend back to air. Meanwhile other crocodiles, if you've staffed the encounter with more than one, are taking second targets. With AC 14 and 85 HP, a single crocodile will drop in two or three rounds of focused fire, but it only needs about that long to drown someone.

Once it's bloodied and the meal is in jeopardy, the crocodile lets go and submerges. It will not pursue onto land. The river belongs to it, and a smart party will mark the bend and find another crossing. A foolish party will return to the same ford the next day and find the crocodile has invited a friend.